The present invention relates to a process vessel for vacuum processing liquid steel comprising a lower part that has submersible pipes located thereon and an upper part, furthermore having a heating apparatus, a feed device, and a waste gas connection arranged at a right angle to the central axis of the vessel, whereby the process vessel has an outer metal jacket and a refractory lining arranged in the interior of the lower part of the vessel, and whereby the metal jacket of the upper part of the vessel, including the waste gas connection, is provided with a water-cooling device and is exposed directly on the interior side to the process conditions prevailing in the interior of the vessel.
JP-A-04 103 713 describes a steel process vessel with the aforesaid features; such a process vessel is used for secondary treatment, e.g. degassing liquid steel, in that the vessel""s submersible pipes located on the lower part are lowered into a pan filled with liquid steel and the liquid steel is suctioned into the process vessel under a vacuum and, after the process phase, is returned to the pan. Provided in the cylindrical middle part of the vessel are connecting branches arranged on an incline for introducing alloy materials and for connecting a burner/heating device.
When very high temperatures occur in the process vessels, these process vessels are provided with a refractory lining at least in their lower part. With regard to the upper part, JP-A-04 103 713, which describes the generic process vessel, suggests providing its metal jacket with a water-cooling device and exposing it directly on the interior side to the process conditions prevailing in the interior of the vessel.
These process vessels also involve the problem of sufficiently cooling the waste gases, and for this purpose a gas cooler is attached to the vessel downstream, which is not addressed in the generic JP-A-04 103 713 and which requires corresponding complexity in terms of construction. The object of the invention is therefore to provide the necessary cooling of the waste gases with the least possible complexity in terms of construction in a process vessel with the aforementioned features.
The realization of this object can be seen from claim 1; advantageous embodiments and further developments of the invention are provided in the subordinate claims.
For this purpose the invention provides that the metal jacket provided with the water-cooling device extends across the waste gas connection and forms a gas cooling segment connected to the waste gas connection of the vessel.
For improving the transfer of heat from the interior of the vessel to the water-cooling of the metal jacket, in accordance with one exemplary embodiment of the invention it can be provided that the metal jacket designed for water cooling has at its surface on the interior of the vessel a coating made from a material with high heat conductivity, whereby the coating preferably comprises copper. This is associated with the advantage of preventing the formation of skull on the water-cooled jacket region, since skull that forms is caused by its own low weight to separate from the walls of the vessel and to fall into the interior of the vessel due to heat elimination that has a shock-type effect. Depending on the exemplary embodiment of the invention, the upper part or even also the middle part can have such a coating.
In its simplest form in terms of the design of the water cooling, it can be provided that the metal jacket has two walls in the region designed for water cooling and is provided with connections for supplying cooling water and for eliminating heated water.
In an alternative embodiment the vessel jacket comprises a vertically-running pipe-to-pipe construction in its region designed for water cooling, whereby the, e.g. round or square, pipes form the intermediate space for conducting the cooling water.
In order to ensure a sufficient connection of the metal jacket provided with water cooling to the region of the vessel provided with a refractory lining, it can be provided that the metal jacket designed for water cooling is provided, at its flange connection to the vessel part having a refractory lining, on the inner side with insulation made of a refractory material that extends across a limited transition region. The insulation arranged in the transition region on the metal jacket designed for water cooling can be thinner than the lining of the adjacent vessel part.
In order to ensure smooth lining of the flange region that is at risk in such an embodiment of the invention, it can be provided that the jacket designed for water cooling, at its flange connection to the vessel part having a refractory lining, is arranged offset to the interior of the vessel by the difference in thickness between the insulation and the lining.